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Context: The electronic properties and optical properties of Cr-doped monolayer WS2 under uniaxial compressive deformation have been investigated based on density functional theory. In terms of electronic structure properties, both intrinsic and doped system bandgaps decrease with the increase of compression deformation, and the values of the bandgap under the same compression deformation after Cr doping are reduced compared with the corresponding intrinsic states. When the compressive deformation reaches 10%, both the intrinsic and doped system band gaps are close to zero. New electronic states and impurity energy levels appear in the WS2 system when doped with Cr atoms. For the optical properties, the calculation and analysis of the dielectric function under each deformation regime of monolayer WS2 show that the compression deformation affects the dielectric function, and when the compression deformation is 10%, the un-doped and Cr-doped regimes show a decrease in ε1(ω) compared to the compression deformation of 8%. For each deformation system, the peak reflections occur in the ultraviolet region. Near the position where the second peak of the absorption spectrum appears, it can be seen that the ability of each system to absorb light gradually decreases with the increase of the amount of deformation and appears to be red-shifted to varying degrees. Methods: This study follows the initial principles of the density functional theory framework and is based on the CASTEP module of Materials-Studio software GGA and PBE generalizations are used to perform computations such as geometry optimization of the model. We have calculated the energy band structure of monolayer WS2 with intrinsic and compressive deformations of 2% and 4% using PBE and HSE06, respectively. The band gap values calculated using PBE are 1.802 eV, 1.663 eV, and 1.353 eV, respectively, and the band gap values calculated with HSE06 are 2.267 eV, 2.034 eV, 1.751 eV. The results show that the bandgap values calculated by HSE06 are significantly higher than those calculated by PBE, but the bandgap variations calculated by the two methods have the same trend, and the shape characteristics of the energy band structure are also the same. However, it is worth noting that the computation time required for the HSE06 calculation is much longer than that of the PBE, which is far beyond the capability of our computer hardware, and the purpose of this paper is to investigate the change rule of the effect of deformation on the bandgap value, so to save the computational resources, the next calculations are all calculated using the PBE. The Monkhorst–Pack special K-point sampling method is used in the calculations. The cutoff energy for the plane wave expansion is 400 eV, and the K-point grid is assumed to be 5 × 5 × 1. Following geometric optimization, the iterative precision converges to a value of less than 0.03 eV/Å for all atomic forces and at least 1 × 10−5 eV/atom for the total energy of each atom. The vacuum layer's thickness was selected at 20 Å to mitigate the impact of the interlayer contact force. [ABSTRACT FROM AUTHOR]

Context: The electronic properties and optical properties of Cr-doped monolayer WS2 under uniaxial compressive deformation have been investigated based on density functional theory. In terms of electronic structure properties, both intrinsic and doped system bandgaps decrease with the increase of compression deformation, and the values of the bandgap under the same compression deformation after Cr doping are reduced compared with the corresponding intrinsic states. When the compressive deformation reaches 10%, both the intrinsic and doped system band gaps are close to zero. New electronic states and impurity energy levels appear in the WS2 system when doped with Cr atoms. For the optical properties, the calculation and analysis of the dielectric function under each deformation regime of monolayer WS2 show that the compression deformation affects the dielectric function, and when the compression deformation is 10%, the un-doped and Cr-doped regimes show a decrease in ε1(ω) compared to the compression deformation of 8%. For each deformation system, the peak reflections occur in the ultraviolet region. Near the position where the second peak of the absorption spectrum appears, it can be seen that the ability of each system to absorb light gradually decreases with the increase of the amount of deformation and appears to be red-shifted to varying degrees. Methods: This study follows the initial principles of the density functional theory framework and is based on the CASTEP module of Materials-Studio software GGA and PBE generalizations are used to perform computations such as geometry optimization of the model. We have calculated the energy band structure of monolayer WS2 with intrinsic and compressive deformations of 2% and 4% using PBE and HSE06, respectively. The band gap values calculated using PBE are 1.802 eV, 1.663 eV, and 1.353 eV, respectively, and the band gap values calculated with HSE06 are 2.267 eV, 2.034 eV, 1.751 eV. The results show that the bandgap values calculated by HSE06 are significantly higher than those calculated by PBE, but the bandgap variations calculated by the two methods have the same trend, and the shape characteristics of the energy band structure are also the same. However, it is worth noting that the computation time required for the HSE06 calculation is much longer than that of the PBE, which is far beyond the capability of our computer hardware, and the purpose of this paper is to investigate the change rule of the effect of deformation on the bandgap value, so to save the computational resources, the next calculations are all calculated using the PBE. The Monkhorst–Pack special K-point sampling method is used in the calculations. The cutoff energy for the plane wave expansion is 400 eV, and the K-point grid is assumed to be 5 × 5 × 1. Following geometric optimization, the iterative precision converges to a value of less than 0.03 eV/Å for all atomic forces and at least 1 × 10−5 eV/atom for the total energy of each atom. The vacuum layer's thickness was selected at 20 Å to mitigate the impact of the interlayer contact force. [ABSTRACT FROM AUTHOR]

The tensile deformation is the most common forming principle in the sheet forming process, but there is a new tube forming process—tube hydro-forging has been developed based on the principle of compression deformation. In addition to the instability problem, a new surface defect—thickness distortion—was found in the compression deformation. In this paper, the wall thickness distortion is analyzed from the point of view of mechanics and deformation. It is revealed that in the low pressure tube hydroforming process, a bending moment exists and leads to some small wrinkles in the straight wall. In the tube hydro-forging, the small wrinkles would develop to the thickness distortion with the increase of compressive deformation. The wall thickness and compressive strain are two major effect factors. It is verified by experiments and simulation. This study helps to recognize the new surface phenomenon in compressive deformation. [ABSTRACT FROM AUTHOR]

{001}〈101〉 texture evolution in Ti–37 mol%Nb (Nb–46.5 mass%Ti) alloy was determined under plane strain compression at the temperatures of 800°C, 950°C, and 1100°C, in which preferential dynamic grain growth (PDGG) took place. At lower temperature and higher strain rate such as 800°C–10−2/s, almost no grain growth occurred in the transverse direction (TD), and the α-fiber + near {111}〈110〉 in the γ-fiber texture was developed, which was a stable orientation as deformation texture. At higher temperature and lower strain rate such as 1100°C–10−3/s, the grain growth along the TD remarkably appeared by grain boundary bulging, and an extremely high pole density of the texture near the α-fiber, especially the rotated cube {001}〈101〉, evolved. A planar dislocation structure with pile-ups appeared and individual dislocations were uniformly distributed in the grains. The rotated cube texture fulfills the conditions of the deformation stability and the low Taylor factor in accordance with the PDGG mechanism. The essential aspect of the mechanism is the preferential growth of grains with a stable orientation for deformation and a low Taylor factor in the given deformation mode. [ABSTRACT FROM AUTHOR]

In today's manufacturing industries, hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and anti-pollution. At this point, aluminum syntactic foams (ASFs) are new-generation engineering composites and come into the upfront as a problem-solver. Owing to their features like low density, sufficient elongation, and perfect energy absorption ability, these advanced foams have been considerably seductive for many industrial sectors nowadays. In this study, an industrial-oriented automatic die casting technology was used for the first time to manufacture the combination of AA7075/porous expanded clay (PEC). Micro evaluations (optical and FESEM) reveal that there is a homogenous particle distribution in the foam samples, and inspections are compatible with the other ASF studies. Additionally, T6 aging heat treatment was operated on one half of the produced foams to explore the probable impact of aging on the compressive responses. Attained results show that PEC particles can be an alternative to expensive hollow spheres used in the previous works. Besides, a favorable relationship is ascertained between the aging treatment and mechanical properties such as compression strength and plateau strength. [ABSTRACT FROM AUTHOR]

Broken gangue from the collapsing roof of a longwall coal panel can be used as the backfilling material for goaf backfilling. The particle size gradation has important influence on the compressive deformation of the gangue backfilling material and particle breakage. The compressive deformation of the gangue backfilling materials at 4 different particle size grades is simulated by PFC3D in this paper. The law of the compressive deformation of the gangue backfilling material, the particle cluster distribution and the variation of the gangue block shape are analyzed. The microscopic mechanism of the compressive deformation of the gangue backfilling material is investigated based on the force-chain distribution. The results indicate that when the gangue backfilling material has a small particle size, the specimen has low porosity and a few amounts of the broken particles can fill the pores of the material. When the particles have relatively large sizes, the specimen has relatively high porosity and the broken particles are unable to completely fill the pores. The loading conditions of the particles can only be changed by the frame structure formed by the large particles. If the proportion of the particle size grade is reasonable, a frame structure forms due to the large particles and the small particles with various particle sizes can fill the pores of the backfilling material. This enhances the deformability of the gangue and decreases the compressive deformation of the backfilling material. After backfilled into the goaf, the backfilling material bears the overburden pressure, which means the process of roof convergence is the process of compressive deformation of the backfill body. That is to say, the stiffer the backfilling material, the better the control effect. The importance of the reasonable proportion of the particle size grade is explained from the aspect of microscopic breakage of the particles, which provides a scientific basis for backfill mining. Image 1 • Influence of particle size on compressive deformation of gangue was studied. • Large particles formed skeleton structure and small particles filled the pores. • Different particle size after crushing led to different compression performance. • Particle breakage was studied from a macroscopic and microscopic point of view. • Small particles increased the coordination number of large particles. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys have become essential materials due to their excellent comprehensive properties as the miniaturization of products in the aerospace and energy fields develops. The complex microstructure and various strengthening mechanisms of nickel-based superalloys make the plastic deformation behavior extremely complicated at the mesoscopic scale. In this paper, compression experiments of nickel-based superalloy samples with different feature sizes (i.e. the sample diameter to grain size ratio, D/d) and different aging times at the mesoscopic scale were carried out. The coupling effect of feature size and δ phase on the compressive deformation behavior was studied. The results show that the δ phase plays a role in precipitation strengthening during compressive deformation at the mesoscopic scale. When D/d is in the range of 9.7–10.9, the flow stress decreases significantly with the increase of grain size, and a “smaller is weaker” size effect appears. When D/d is less than 9.7, the flow stress increases with the grain size, and a “smaller is stronger” size effect appears. Considering grain boundary strengthening, solid solution strengthening, and precipitation strengthening, a size effect model of flow stress was established. The calculated values were in good agreement with the experimental values. The inhomogeneity of the end surface and side surface increases with the decrease of feature size and the decrease of aging time. The presence of the δ phase reduces the inhomogeneous deformation of nickel-based superalloys during compressive deformation at the mesoscopic scale.

• Bearing capacity and energy absorption characteristics of the optimized AlSi10Mg structure are significantly enhanced. • Finite element calculation model used in this paper accurately describes the mechanical behavior of AlSi10Mg structure. • Fracture features of AlSi10Mg porous structure indicate a ductile as well as a brittle failure under compressive load. • Normalized energy absorption helps designers select the one structure most suitable for a given application. In order to correctly understand the mechanical behavior, damage mode and damage mechanism of AlSi10Mg optimized structure under compressive load, a series of experimental and simulation studies were carried out. The stress-strain response, bearing capacity, energy absorption characteristics, damage mode and mechanism of the structure are analyzed and discussed. The results show that AlSi10Mg porous structure has obvious strain hardening effect, but no obvious strain rate effect. The volume fraction of AlSi10Mg porous structure increased from 9.43% to 22.15%, and its bearing strength increased from 22.34 MPa to 50.98 MPa. The optimized design structure is complex in this paper, which eliminates undesirable failure modes, and the benefit of high specific energy absorption is retained. The experimental and simulation results show that shear failure is the main cause of structural damage, and the normal of the failure section and the load action direction are roughly inclined at an angle of 45° ∼ 55°. The research results can provide an important reference for the optimal design of porous metal structure. [ABSTRACT FROM AUTHOR]

For engineering materials, it is important to search for strategies to enhance certain combinations of mechanical properties, because many performances, such as strength and toughness, are mutually exclusive. Effective strategies have evolved in the biological tissues of many plants and animals to construct composite materials with unique combinations of mechanical properties. One impressive example is found in the hammer-like appendages of mantis shrimp, which are exceptionally resistant to crushing because they must withstand the reaction forces created when attacking prey. In this paper, quasi-static compression tests, advanced microscopic observation, and spectroscopic analysis were employed to identify a series of characteristic changes, including changes in mineral composition and arrangement of chitin fibers, and the resulting toughening mechanisms are also examined. The combination of experiments and finite element analysis revealed that by combining different fiber arrangements and components in adjacent macroscopic layers, longitudinal stress could be shifted to the lateral direction, hence efficiently enhancing longitudinal compression resistance while avoiding catastrophic failure. Overall, these findings further the understanding of the fiber structure and toughening mechanism of appendages, which may serve as a foundation for the development of tough bioinspired composites.

The webs such as paper, plastic film and thin metal are produced by Roll-to Roll manufacturing system, and are wound into a roll in the final process of this system. However, if the winding conditions of the web are inappropriate, the defects such as gage band, wrinkle and slippage will occur in wound roll, and then quality of products is significantly reduced. In previous studies, some analysis models of in-roll stress considering various factors, have been established to predict the defects. However, as far as authors know, there is few research regarding the gage band. In particular, the plastic films used for high functional flexible devices are being thinner, the defects can occur easily. In this paper, the in-roll stress analysis considering the web thickness variation in width direction and compressive deformation of web in the radial direction using the Hertz contact theory is presented. Moreover, optimization of winding conditions is conducted to prevent simultaneously the gage band, wrinkle and slippage. As a result, it was confirmed that the presented analysis can estimate the radial stress distribution of wound roll in the width direction. And, the effectiveness of optimized wind-up tension is verified theoretically and experimentally.

Electromagnetic interference (EMI) cause the equipments used in electronics and avionics industries to either deteriorate or malfunction. Therefore, EMI shielding is essential to ensure electronics equipment safety. The present investigation explores the EMI shielding effectiveness of micro-size cenosphere (2 wt.%, 4 wt.%, and 6 wt.%) filled aluminum matrix syntactic foams. The aluminum matrix syntactic foams were fabricated using stir-casting. The prepared samples were studied for their EMI shielding, microstructural characterization, compressive deformation behavior, and hardness. The cenosphere-filled aluminum syntactic foam exhibited better EMI shielding effectiveness, varied from −41.38 dB to −56.68 dB measured in the frequency range 8 to 12 GHz. This is due to microwave absorption and the dielectric nature of porous cenosphere fillers in the syntactic foam. The highest plateau strength 316.48 MPa and compressive yield strength of 289.53 MPa was achieved in 6 wt% cenosphere-filled syntactic foam. The microstructural study showed the presence of cenospheres in spherical form with homogeneous distribution. The observation shows good bonding between the matrix and cenosphere filler element. The micro-hardness measurement varied from 114 HV to 125.6 HV for the cenosphere filled syntactic foam (up to 4 wt %); further increasing the cenosphere wt% reduced the hardness. The XRD analysis showed the presence of reaction compounds AlSiO2, and Al2SiO5 which enhanced the brittleness in the syntactic foams. [ABSTRACT FROM AUTHOR]

In this paper rolled AZ31 magnesium alloy was deformed by interrupted in situ compressive tests. Compressive and re-compressive tests were conducted along rolling direction (RD). It is discovered that the yield strength of re-compression is enhanced due to grain refinement by {10–12} tensile twins. Twinning activation and evolution are evidenced by electron backscatter diffraction. Correlations with grain orientation and boundary misorientation are observed in the region of twins that arise at grain boundaries. The distributions of grain boundary misorientation associated with twin nucleation are mapped. It is found that nucleation of twin is mainly controlled by the initial texture, and is more easy at low misorientation grain boundaries. The growth of twins depend on two modes: the thickening of the existing twin lamellae and new twins is nucleated at grain boundary. With increasing compressive strain, the growth and coalescence of twins eventually encompassed the whole grain. Meanwhile, the basal texture is weaker after compression due to the propagation and coalescence of tensile twins. [ABSTRACT FROM AUTHOR]

In order to correctly understand the bearing capacity, failure mode and failure mechanism of AlSi10Mg porous optimized structures at different strain rates under compressive load, a series of experimental and simulative studies were carried out. Through quasi-static and modified Split Hopkinson Pressure Bar (SHPB) experiments, the damage failure modes of the AlSi10Mg porous structures with three different volume fractions are obtained at different strain rates. The stress-strain curves of AlSi10Mg porous structures obtained from the experimental results at different high strain rates show that its mechanical behavior is not sensitive to strain rates. Combined with meso-structure analysis and high-precision numerical simulation, it is found that the shear failure of AlSi10Mg porous structures due to relative dislocation along the inclined section under axial compressive load is the most direct cause of failure, which reveals its failure mechanism. Combining experimental research and theoretical analysis, the energy absorption characteristics and influencing factors of AlSi10Mg porous structures are determined at different strain rates. At the same time, the prediction models of dynamic elastic modulus and dynamic compressive strength of AlSi10Mg porous structures are constructed, which accurately describe the variation law between dynamic elastic modulus, dynamic compressive strength and structural volume fractions. These research works in this paper will provide an important reference for the structure optimal design of lightweight, strong energy absorption and impact resistance. [ABSTRACT FROM AUTHOR]

The compressive deformation of backfill materials is large due to the large mining depth of coal seams and high mining-induced stress during the deep backfill mining. Therefore, the controlling effect on strata movement significantly differs from that in shallow coal seams. The research aims to explore the influences of the compressive deformation of backfill materials on the strata movement and stress evolution in deep backfill mining. For this purpose, the backfill panel in Xinjulong Coal Mine, Shandong Province, China was taken as an engineering case study; the changes in displacement, structural evolution, and stress distribution of overlying strata in the panel under compression ratios of backfill materials of 70%, 40%, and 20% were investigated. In addition, the influences of different compressive deformations of the backfill materials on the controlling effect on overlying strata were compared and investigated. The results showed that the displacement of overlying strata in the backfill panel decreases with the decreasing compression ratio: the maximum displacement of overlying strata decreases from 24.32 to 13.74 and 6.83 mm as the compression ratio is reduced from 70 to 40%, and 20%, respectively. Relative to the overlying strata at a compression ratio of 70%, the vertical displacements at compression ratios of 40 and 20% separately decrease by 43.5 and 71.9%. The lower the compression ratio of backfill materials, the better the control of overlying strata. The results provide theoretical support for optimizing the performance of backfill materials in deep backfill mines and controlling the ground pressure in the stope. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the deformation behavior and texture evolution during uniaxial compression in an extruded Mg–1Gd alloy with a typical 〈2−1−11〉 fiber texture using the electron backscattering diffraction (EBSD) technique. Extension twinning and basal slip are the dominant deformation modes in the early stage of compressive deformation, which are responsible for the remarkable change of texture components. With increasing strain, the texture is changed from the 〈2−1−11〉 into the 〈0001〉 fiber texture component mainly due to the gradual rotation of c-axes towards the compressive direction caused by basal slip. [Copyright &y& Elsevier]

Abstract: This paper deals with the compressive deformation behaviour of AA2014–10wt.% SiCp composites synthesized by stir casting technique. The response of the composites was studied over the strain rates of 0.01–10/s and the temperature range of 200–500°C. The flow stress increased with increasing strain rates while increasing temperature produced a reserve effect. The flow behaviour of the samples has been represented by Zener–Holloman parameter Z that was affected by strain rate and temperature in a manner similar to that of the flow stress. The lowering of Z value with increasing temperature is essentially due to extensive dynamic softening. The stress exponent (n) and deformation activation energy (Q) have been evaluated by linear regression analysis. The activation energy for the hot deformation of the composite was found to be 168kJ/mol, which is higher than bulk self diffusion of pure Al i.e., 142kJ/mol. The higher activation energy required for the flow of composite was mainly due to the alloying elements present in the Al matrix and dispersion of SiC particles that restricted the flow of material. [Copyright &y& Elsevier]

An investigation was performed on the effects of semi-solid compression parameters, such as strain rate, compression temperature and heating time at these temperatures on deformation behaviors of two kinds of ZA27 alloys, one was modified by Zr and the other was unmodified. The results indicate that with the increasing of the strain, the stress of the modified composite first sharply increases to a peak value, then dramatically decreases to a peakeau value, and again increases till the end of deformation. But for the unmodified, after being up to a peak value, the stress only decreases slowly. As the compression temperature or the heating time decreases, or the strain rate increases, the stress level and the cracking degree of these two kinds of alloys increase. Under the same deformation conditions, the stress level and the cracking degree of the unmodified alloy are higher than those of the modified one. But there is an exception that the stress level of the unmodified alloy is minimum and smaller than that of them modified one when deformed at the low temperature of 450°C. These phenomena were mainly discussed through analyzing the microstructures under different conditions and the deformation mechanisms at different deformation stages. [ABSTRACT FROM AUTHOR]

Large unique block Ni–Cr–Al superalloy foam was fabricated using a combination method of powder-alloying, multi-sheet stacking, and hot compression processes. Subsequently, the compressive properties and deformation behaviors of multi-sheet stacked block metallic foam were investigated from room temperature to 1073 K. The analysis of the resulting structural characteristics of the block foam showed that the interfaces between the sheets have complex strut interactions, such as contacted (deformed) and intersected struts. The relative density was measured as 2.93% for sheet foam and 4.90% for block foam. The compressive deformation of sheet and block Ni–Cr–Al foams showed the typical compressive stress–strain curves of plastically deformable metallic foams regardless of foam type. However, different deformation behaviors in the plateau regions were detected based on the type of foam. It is noteworthy that the yield strength of block foam showed a relatively lower value than that of sheet foam, even though the block foam had higher relative density. The existence of unique interfaces in the multi-sheet stacked block foam may have affected strength and plastic deformation. Finally, distinct compressive behaviors related to the structural and microstructural characteristics of block Ni–Cr–Al foam are discussed. [ABSTRACT FROM AUTHOR]

An open‐cell metallic foam is newly manufactured using the electrostatic powder spraying (EPS) process, and its room temperature compressive and energy absorption properties are investigated. EPS is a process that uses electrostatic forces. The powder is negatively charged by applying direct current high voltage and undergoes electrostatic spraying on a positively charged polyurethane pre‐form. To control relative density (ρ*/ρ), three different spray amounts are applied (2.5, 3.5, and 4.5 kg m−2). Also, the relative density is measured to increase constantly with the spray amount. The room temperature compressive curves of the EPS foams represent the typical compressive stages (linear elastic, plastic collapse, and densification) of metallic foam. The plateau strengths of the EPS foams measure 0.48 MPa (spraying amount: 2.5 kg m−2), 0.76 MPa (spraying amount: 3.5 kg m−2), and 1.23 MPa (spraying amount: 4.5 kg m−2), respectively. Also, EPS 316L foam with the smallest spray amount has a lower energy absorption amount compared with other types of foam. This study also discusses the compressive and energy absorption behaviors of an open‐cell metallic foam manufactured using the EPS process in relation to its structural and microstructural characteristics. [ABSTRACT FROM AUTHOR]

In this study, the compressive deformation of crushed sandstone was tested using a crushed rock deformation-seepage test system, and the effects of various factors, including crushed rock grade, grade combination, water saturation status, and stress loading method (i.e., continuous loading or cyclic loading and unloading), on the compressive deformation of crushed sandstone was analyzed from four perspectives including stress-strain, bulking coefficient, deformation mechanism and energy dissipation. The results indicate that the stress-strain relations of crushed sandstone are closely associated with all factors considered, and are well represented by exponential functions. The strain observed for a given applied stress increased with increasing crushed rock grade throughout the loading period. Crushed sandstone grades were combined according to a grading index (n), where the proportion of large-grade rocks in the sample increased with increasing n. The bearing capacity of a water-saturated crushed sandstone sample with n = 0.2 was less than that of an equivalent dry sample for a given applied stress. The stress-strain curve of a water-saturated crushed sandstone sample with n = 0.2 under cyclic loading and unloading was similar to that obtained under continuous loading. Observation and discovery, the deformation mechanism of crushed sandstone was mainly divided into four stages, including crushing, rupture, corner detachment and corner wear. And 20% of the work done by testing machine is used for friction between the crushed sandstone with the inner wall of the test chamber, and 80% is used for the closing of the void between the crushed sandstone, friction sliding, crushing damage. [ABSTRACT FROM AUTHOR]

Water removal rate during drying depends on the microstructural pathways of water migration from inside the food materials. The water removal rate also depends on the mechanical properties of plant tissue. There is no literature that shows the interrelationship between viscoelastic property and transport phenomena during drying. In this study, the influence of viscoelastic property of plant-based food material on transport phenomena during drying has been experimentally investigated. Granny Smith apple, pears, and beet root has been taken as the sample in this study. A 2 kN Instron universal testing machine and ImageJ software were used in order to measure and analyze the viscoelasticity of the samples. Three different fruits Granny Smith apple, pears, and beet root show different viscoelastic properties along with different energy loss due to hysteresis. A positive relationship was found between energy loss due to viscoelastic nature of materials and drying kinetics. This correlation can be explained by the nature of the cell wall stiffness that facilitates or hinders the water migration in mechanical and thermal energy applications. [ABSTRACT FROM AUTHOR]

In order to examine the effect of microballoons type on microstructure and compressive deformation behaviour of aluminum syntactic foam, alumina reinforced and cenosphere reinforced aluminum syntactic foams have been made through stir-casting technique. Alumina microballoons reinforced aluminum syntactic foam (AMRASF) has been developed using stir casting technique. Volume fraction of alumina microballoons in AMRASF varies in the range of 0.39–0.74. The compressive deformation behavior of these AMRASF is compared with that of cenosphere reinforced aluminum syntactic foam (CPRASF). The AMRASF does not exhibit clear plastic collapse stage as observed in case of CPRSAF. It is further noted that AMRASF shows the existence of work hardening phenomena after yielding but CPRASF does not show any significant work hardening after yielding even at higher relative densities of foam. This is explained on the basis of characteristics of alumina microballoons and cenospheres and interface characteristics between matrix and respective microballoons used. Effect of individual microballoons’ characteristics on the foam properties has also been explained. [ABSTRACT FROM AUTHOR]

Water removal during drying depends on the pathway of water migration from food materials. Moreover, the water removal rate also depends on the characteristics of the cell wall of plant tissue. In this study, the influence of cell wall properties on porosity and shrinkage of dried product was investigated. Cell wall stiffness depends on a complex combination of plant cell microstructure, composition of food materials and the water-holding capacity of the cell. In this work, a preliminary investigation of the cell wall properties of apple was conducted in order to predict changes of porosity and shrinkage during drying. Cell wall characteristics of two types of apple (Granny Smith and Red Delicious) were investigated under convective drying to correlate with porosity and shrinkage. A scanning electron microscope (SEM), 2kN Intron, pycnometer and ImageJ software were used in order to measure and analyse cell characteristics, water holding capacity of cell walls, porosity and shrinkage. The cell firmness of the Red Delicious apple was found to be higher than for Granny Smith apples. A remarkable relationship was observed between cell wall characteristics when compare with heat and mass transfer characteristics. It was also found that the evolution of porosity and shrinkage are noticeably influenced by the nature of the cell wall during convective drying. This study has revealed a better understanding of porosity and the shrinkage of dried food at microscopy (cell) level, and will provide better insights to attain energy-effective drying processes and improved quality of dried foods. [ABSTRACT FROM AUTHOR]

The dynamic recrystallization (DRX) behavior of continuous columnar-grained (CCG) CuNi10Fe1Mn alloy was investigated by hot compression along the solidification direction (SD) and perpendicular to the solidification direction (PD). Specimens were compressed to a true strain of 0.8 at temperatures ranging from 25°C to 900°C and strain rates ranging from 0.01 to 10 s. The results indicate that DRX nucleation at grain boundaries (GBs) and DRX nucleation at slip bands (SBs) are the two main nucleation modes. For SD specimens, C-shaped bending and zig-zagging of the GBs occurred during hot compression, which made DRX nucleation at the GBs easier than that at the SBs. When ln Z ≤ 37.4 ( Z is the Zener-Hollomon parameter), DRX can occur in SD specimens with a critical temperature for the DRX onset of ~650°C and a thermal activated energy ( Q) of 313.5 kJ·mol. In contrast, in PD specimens, the GBs remained straight, and DRX nucleation occurred preferentially at the SBs. For PD specimens, the critical temperature is about 700°C, Q is 351.7 kJ·mol, and the occurrence condition of DRX is ln Z ≤ 40.1. The zig-zagging of GB morphology can significantly reduce the nucleation energy at the GBs; as a result, DRX nucleation occurs more easily in SD specimens than in PD specimens. [ABSTRACT FROM AUTHOR]

The hot compression behaviour of AA2014 alloy having 10 wt% SiC particles was studied over a wide range of temperatures (ambient to 400 °C) and strain rates (0.01-10/s). The results were compared with those obtained from identical tests performed on the base alloy to understand the effect of the SiC particle reinforcement. Processing maps were generated using dynamic materials model from the flow stress of the samples. Microstructures of the deformed samples suggest the occurrence of dynamic recrystallization at high temperatures and low strain rate. Flow localization and adiabatic shear bands were observed at higher strain rates and temperatures. The lack of cohesion between SiC particles and the matrix was found to be responsible for the deteriorating deformation behavior of the composite over most of the processing domains. The activation energy for high temperature deformation in the presence of the SiC particles in the alloy was found to be significantly higher than that of the matrix. This makes deformation processing of the composite more difficult than that of the matrix. [ABSTRACT FROM AUTHOR]

The high-temperature deformation and damage behavior of ultrafine-grained (UFG) Cu produced by equal channel angular pressing (ECAP) were investigated and compared at two strain rates of 10-2 s-1 and 10-3 s-1. It is found that the strain rate has an obvious effect on the deformation and damage behavior of UFG Cu, especially at the testing temperatures near and above recrystallization. In general, the lower the strain rate, more universally grain coarsening takes place, the lower the yield stress and steady flow stress are, and more aggravated the degree of deformation damage becomes. [ABSTRACT FROM AUTHOR]